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Atomic structures of an entire contractile injection system in both the extended and contracted states.

ABSTRACT: Contractile injection systems are sophisticated multiprotein nanomachines that puncture target cell membranes. Although the number of atomic-resolution insights into contractile bacteriophage tails, bacterial type six secretion systems and R-pyocins is rapidly increasing, structural information on the contraction of bacterial phage-like protein-translocation structures directed towards eukaryotic hosts is scarce. Here, we characterize the antifeeding prophage AFP from Serratia entomophila by cryo-electron microscopy. We present the high-resolution structure of the entire AFP particle in the extended state, trace 11 protein chains de novo from the apical cap to the needle tip, describe localization variants and perform specific structural comparisons with related systems. We analyse inter-subunit interactions and highlight their universal conservation within contractile injection systems while revealing the specificities of AFP. Furthermore, we provide the structure of the AFP sheath-baseplate complex in a contracted state. This study reveals atomic details of interaction networks that accompany and define the contraction mechanism of toxin-delivery tailocins, offering a comprehensive framework for understanding their mode of action and for their possible adaptation as biocontrol agents.

SUBMITTER: Desfosses A

PROVIDER: S-EPMC6817355 | biostudies-literature | 2019 Nov

REPOSITORIES: biostudies-literature

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Atomic structures of an entire contractile injection system in both the extended and contracted states.

Desfosses Ambroise A Venugopal Hariprasad H Joshi Tapan T Felix Jan J Jessop Matthew M Jeong Hyengseop H Hyun Jaekyung J Heymann J Bernard JB Hurst Mark R H MRH Gutsche Irina I Mitra Alok K AK

Nature microbiology 20190805 11

Contractile injection systems are sophisticated multiprotein nanomachines that puncture target cell membranes. Although the number of atomic-resolution insights into contractile bacteriophage tails, bacterial type six secretion systems and R-pyocins is rapidly increasing, structural information on the contraction of bacterial phage-like protein-translocation structures directed towards eukaryotic hosts is scarce. Here, we characterize the antifeeding prophage AFP from Serratia entomophila by cry ...[more]

PMID: 31384001

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Project description:Myophage Mu is a representative of contractile nanomachines with a simple tail baseplate. It has the capacity to infect a range of intestinal bacteria and has extensive applications in genetic engineering research. Nevertheless, a comprehensive understanding of the entire structure and contractile mechanisms of Mu remains elusive. Using cryo-electron microscopy (cryo-EM), we resolved the asymmetric structures of Mu in both its extended and contracted states, the latter of which lacked the tail baseplate, at near-atomic resolutions. We built the atomic models for the extended Mu, encompassing the head, the connector complex, the tail, and the simple baseplate. It is noteworthy that we identified the position and structure of the tail tube initiator protein gp43 (referred to as the DNA circularization protein). The protein gp43 plays a crucial role not only in the baseplate assembly and DNA circularization but also in stabilizing the wedge-hub connection and mediating tail contraction. Except for the baseplate structure, the structural comparison of Mu in its extended and contracted states revealed that only the tail sheath protein gp39 and the C-terminus of the tail terminator protein gp37 undergo notable conformational changes to accommodate the tail contraction, whereas the remaining protein components remained unchanged. Our structures exhibited conserved properties among the majority of myophages, thereby providing valuable insights into the contraction mechanisms across myophages and contractile injection systems (CISs).ImportanceDespite extensive study, the asymmetric structures of phage Mu, a highly effective transposable myophage, remain unknown. In this study, we present the high-resolution structures of Mu in both its extended and contracted states. The comparison of the two structures allows for the illustration of detailed conformational changes of the head-to-tail complex during the process of tail contraction. The contraction mechanism of Mu is highly conserved and widely adapted to all contractile nanomachines that share common structural features with Mu.

Dataset Information

Atomic structures of an entire contractile injection system in both the extended and contracted states.

Publications

Atomic structures of an entire contractile injection system in both the extended and contracted states.

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